#define _CRT_SECURE_NO_WARNINGS

#include<iostream>
#include<string>
using namespace std;

int main()
{
	string s1;
	cout << s1 << endl;

	string s2("abc");
	cout << s2 << endl;

	string s3(s2);
	cout << s3 << endl;

	string s4(3, 'a');
	cout << s4 << endl;

	return 0;
}

